The raspberry pi zero w was introduced several years ago. I bought one shortly after it was introduced to see how it would compare to the standard pi zero. I have a couple of these now, purchased when they were on super discount at stores like Microcenter. Five bucks for a linux computer is hard to pass by!
The wireless did work but had limited range due to the small antenna on the board.
As with the regular zero, the little video port requires an adapter to work with a standard cable. You also may need a usb hub if you want to connect mice and keyboards. There is a board you can clip to the top of the zero that gives it more usb ports and such but of course that doubles the mass.
All in all, this is a great little board for embedded use but not so much for a desktop.
Where this board can shine is in the form of an embedded video and still image recorder. There is a camera port, which naturally requires a special cable because it is downsized. There is enough RAM to run linux and command line tools to capture images and write them to the sd card (raspistill for example). The built in wifi means you can run an ftp server on the board, and read the images out wirelessly or even connect wirelessly via ssh.
I have seen postings online where folks have used the pi zero for model rocket telemetry or data logging and it works ok from a battery.
The IO pins are the same as the standard PI so the same hats could be used though I have not tried this.
So, the use of linux means this is probably not a great platform for driving hard real time systems. But with some software, it can be made into an intelligent camera system for the balloon, and controlled by another board to get it to take pictures and send them to the radio.